Method of manufacturing hollow, circular-shaped workpieces

ABSTRACT

Method of manufacturing hollow, circular-shaped workpieces. A hollow ingot is formed by centrifugally casting chromium steel, a chemically heat-treatable steel, or from other steels. The centrifugally cast hollow ingots are formed using a rolling, forging or die-forging mechanism, the thus obtained tubes or annuli are divided into sections, and the sections are then profile-rolled, forged or die-forged, machined by metal cutting methods, subsequently heat-treated to obtain optimum hardness, and after tempering finished by grinding, superfinishing, lapping and polishing or by combination of these finishing methods.

United States Patent Sommer et al.

[ Dec. 23, 1975 Dec. 4, 1973 METHOD OF MANUFACTURING HOLLOW, CIRCULAR-SHAPED WORKPIECES Inventors: Karel Sommer; Jiri Zdrazil; Milan Kubinek, all of Brno; Jarolim Bahna, Illava; Stanislav Kyselica, Trencianska Tepla; Frantisek Habrovec; JiriSkarek, both of Brno, all of Czechoslovakia ZKL Zavody na valiva loziska a traktory, narodni podnik, Brno, Czechoslovakia Filed: Aug. 1, 1974 Appl. No; 493,752

Assignee:

Foreign Application Priority Data Czechoslovakia 8331-73 US. Cl 29/,l48.4 R; 29/417; 29/527.6;

1.11.1311... .1 B211) 53/12; 3211-! 1/12 Field of Search 29/1484 R, 148.4 c, 417, 29/527.6, 558; 148/2, 3

References Cited UNITED STATES PATENTS 11/1923 Lothrop 29/1484 R X 9/1970 DiPonio 29/l48.4 R x 3,714,694 2/1973 Dobson 29/1484 R 3,737,965 6/1973 Knapp 29/l48.4 R

FOREIGN PATENTS OR APPLlCATlONS 412,868 7/1934 United Kingdom 29/148.4

Primary Exan1inerVictor A. DiPalma 18 Claims, 3 Drawing Figures METHOD OF MANUFACTURING HOLLOW,

. CIRCULAR-SHAPED WORKPIECES The present invention relates to a method for the manufacture of hollow, circular-shaped workpieces made from a standard bearing steel or normal composition or from a chemically heat-treatable steel or from other steels, e.g. from steels according to the Czechoslovakian Patent Specification No. 147,484. The method may be effected by hot as well as by cold forming and is particularly suitablefor the manufacture of bearing races.

The best known bearing manufacturers are using conventional bearing steel for the manufacture of bearing races, such bearing steel containing 1% of carbon and l to 1.5% of chromium. The manufacture proper of races is accomplished by turning them from bars, tubes, or bars forged to semi-products, or by rolling-out ring blanks. Owing to the workability as well as to the necessity of predetermined internal structure prior to hardening, a heattreatment of the race semi-products combined with spheroidizing soft annealing is necessary. After being austenitized at a suitable temperature, races machined by a metal cutting method are hardened and tempered. The turning operation may be partially substituted by cold rolling-out of the semiproducts.

According to the latest technology, tubes manufactured by centrifugal casting are used as starting mate rial, such tubes are first divided into individual slugs and are then formed by rolling-out or by forging. This method of manufacture, in contradistinction to other known methods, is advantageous mainly in that it eliminates several processing stages within the metallurgical portion of production, its only drawback being that it can be conveniently utilized predominantly with rings of greater diameter.

The method of manufacture of hollow, circularshaped workpieces according to the invention improves the previously described method of manufacture of bearing races from centrifugally cast hollow ingots using a conventional bearing steel or a chemiw cally heat-treatable steel, e.g. a carburizing steel or other steels, e.g. a steel whose structure is the subject of the US. Pat. No. 3,859,146. The principle of the invention resides in that centrifugally cast hollow ingots or individual annuli or other rotary components in the form of bodies of revolution with profiled surface are formed using a rolling, forging or die-forging mechan ism, after which the obtained tubes or annuli are divided into sections which are then profile-rolled, forged or die-forged, then machined by metal cutting methods, subsequently heat-treated to obtain optimum hardness, and after tempering are finished by grinding, s'up'erfi'nishing, lapping and polishing or bya combination of these finishing methods. Tubes obtained by' ing attachment or by a metal cutting method with a simultaneous removal of the slag-contaminated material layer. Workpieces made from chrome-steel or from steel according to the US. Patent No. 3,859,146 are submitted to spheroidizing annealing, are then machined by a metal cutting method, after which they are heated to austenitizing temperature for subsequent hardening. Work-pieces from chemically heat-treatable steel are first machined by applying a metal cutting method, then the surface is submitted to a'chemical heat-treatment with subsequent single or double hardening and tempering. The races are profile-rolled with finishing allowances, after which they are heated to austenitizing temperature for. subsequent hardening. Components made from steel suitable for chemical heat-treatment are formed by profile-rolling with finishing allowances. The semi-products of the components are first heated to a temperature corresponding to the hardening temperature, then the ring-rolling or ring-forging is carried out with subsequent hardening and tempering. The components are first heated to the austenite temperature zone, then cooled down to a temperature corresponding to approximately the longest latent periodof the decomposition of undercooled austenite, after which profile-rolling, rolling, forging or die-forging with subsequent hardening are performed. The semi-products are'formed by ring-rolling or forging, down to a temperature corresponding to the hardening temperature, after which they are machined in the hardened state using a metal cutting method, and are then tempered. The semi-products of components having a greater length, compared with the wall thickness of the final forging, are first die-forged to the required cross-section, whereupon they are turned through an angle of between the bottom-die and the punch within a single working stroke of the pressram and are sized at the bottom dead center of the ram stroke. Annular shaped semiproducts having a greater length compared to the wall thickness of the forging are first die-forged to a cross-section corresponding to the annulus of the outer bearing-races and partly to the annulus of the inner bearing races, after which the common blanks obtained are sheared, the annulus for outer races is turned through an angle of 90, whereas the annuli for inner races are turned through an angle of 90 after the width has been die-forged to the required cross-section. The ring blanks are profile-rolled between rolls whose operating surfaces are identical with the shape of finished races. It is also possible to die-forge the race blanks in forming dies whose operating surfaces are identical with the shape of finished races. The shape on the outer surface of the races is formed between profile rolls and the mandrel, the width and the passage through the finished races being identical with the starting semi-products of the races.

The methods of manufacture presented herein and falling within the principle of the invention enable the attaining of a high quality of the product, especially of roller bearings. The main effect resulting from the utilization of the invention is that when using, in particular,

through an angle of 90 is advantageous particularly for the manufacture of outer and inner roller bearingraces.

The drawings illustrate a few examples of the application of the method according to the invention.

In the drawings:

FIG. 1 depicts successive steps in the process of manufacturing an outer rolling bearing-race;

FIG. 2 depicts successive steps in the process of manufacturing inner bearing-races; and

FIG. 3 represents the process of manufacturing an annular component with grooves on the outer circumference.

The manufacture of an outer race, as depicted in FIG. 1, involves the following steps. A hollow ingot is centrifugally cast; ingot 1 has a slag-contaminated central layer 2. Layer 2 is removed first, then the ingot 1 is rolled into a tube 3 from which individual annuli 4 are sheared off. After heating to austenitizing temperature suitable for the steel used, and after cooling down the temperature over a period the maximum latent period of the decomposition of undercooled austenite, this annulus 4 is rolled out between the rolling disk 5 and the rolling mandrel 6, the rolled product 7 is submitted to subsequent hardening and tempering, and the resulting semi-product 8 of the outer bearing race is finished by grinding, super-finishing or by lapping.

As shown in FIG. 2, a similar procedure is also used for the manufacture of an inner bearing-race 20. A centrifugally cast hollow ingot l with its slag-contaminated central layer 2 is rolled to form tube 13. The slag layer 2 is simultaneously removed in one turning operation using a turning tool 14; the individual annuli 15 are separated with the aid of a parting-off tool 16. The annuli 15 are then cold rolled between a rolling disk 17 and a rolling mandrel 18; the resulting rolled products 19 are hardened and tempered and the thus obtained semi-products are then finished to form inner bearing races 20.

When producing workpieces with circumferential grooves, there is employed the method shown in FIG. 3. A centrifugally cast hollow ingot 21 made from chemically heat-treated steel with a groove 22 on the outer surface and with a slag-contanimated central layer 23 is used. Layer 23 is removed using a turning tool 24; simultaneously therewith, with the aid of a parting-off tool, 25 the individual annuli 26 are separated. Annuli 26 are then die-forged between forming dies 27 and 28. The resulting semi-product 29 of the workpiece has an internal flash 30, which is then machined by a metal cutting method. After having been chemically heat-treated and hardened, the semiproduct is finished to specified dimensions.

Although the invention is illustrated and described with reference to a plurality of preferred embodiments thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a plurality of preferred embodiments, but is capabale of numerous modifications within the scope of the appended claims.

What is claimed is:-

1. A method of manufacture of hollow, circularshaped workpieces, comprising centrifugally casting hollow ingots from a bearing steel, reducing the ingot to form a tube, dividing the tube into sections, profileforming the sections, then machining the formed sections by metal cutting methods, subsequently heattreating the machined formed sections to obtain optimum hardness, and after tempering finishing the prodnot by at least one of the steps of grinding, superfinishing, lapping and polishing.

2. A method according to claim 1, wherein tubes obtained by rolling are divided into annuli by a cutting method for further processing to final products.

3. A method according to claim 1, comprising removing the inner slag contaminated-layer from within the holes of the hollow workpieces prior toshaping them.

4. A method according to claim 2, wherein the tubes obtained by rolling are divided into semi-products each of which serves for the fabrication of two or more parts.

5. A method according to claim 2, comprising removing the inner slag-contaminated layer simultaneously with the dividing of the tube. V 6. A method according to claim 1, wherein workpieces made from chrome-steel are submitted to spheroidizing annealing, then machined by a metal cutting method, whereupon they are heated to austenitizing temperature for subsequent hardening.

7. A method according to claim 1, wherein workpieces from chemically heat-treatable steel are first machined applying a metal cutting method, then the surface is submitted to a chemical heat-treatment with subsequent hardening and tempering.

8. A method according to claim 1, wherein the races are profile-rolled with finishing allowances, after which they are heated to austenitizing temperature for subsequent hardening.

9. A method according to claim 8, wherein the components are made from steel suitable for chemical heattreatment and are formed by profile-rolling with finishing allowances.

10. A method according to claim 1, in which bearing steels are used, and wherein a high-temperature mechanical treatment is applied, wherein the semiproducts of the components are first heated to a temperature corresponding with the hardening temperature, then ring-forming is accomplished, with subsequent hardening and tempering.

11. A method according to claim 1, in which bearing steels are used, and wherein a low-temperature mechanical treatment is applied, wherein the components are first heated to the austenite temperature zone, then cooled down to a temperature corresponding to approximately the longest latent period of the decomposition of undercooled austenite, after which the profileforming with subsequent hardening are performed.

12. A method according to claim 1, wherein the semi-products are formed by ring-forming at a temperature down to a temperature corresponding to the hardening temperature, after which they are machined in a hardened state using a metal cutting method, and

then tempered.

13. A method according to claim 1, wherein semiproducts of components having a greater height, compared with the wall thickness of the final forging, are first die-forged to the required cross-section, after which they are turned through an angle of between the bottom-die and the punch of a press ram within a single working stroke of the press ram and are sized in the bottom dead center of the ram stroke.

14. A method according to claim- 13, wherein annular shaped semi-products having a greater height compared to the wall thickness of the forging are first dieforged to a cross-section corresponding to the annulus of the outer bearing-races and partly to the annulus of the inner bearing-races, after which the thus obtained common blanks are sheared, the annulus for outer races is turned through an angle of 90.

- 15. A method according to claim 13, wherein annular shaped semi-products having a greater height compared to the wall thickness of the forging are first dieforged to a cross-section corresponding to the annulus of the outer bearing-races and partly to the annulus of the inner bearing-races, after which the thus obtained common blanks are sheared, the annulus for an inner race is inverted by an angle of 90 after the width had been die-forged to the required cross-section.

16. A method according to claim 13, wherein the ring blanks are profile-rolled between rolls, whose operatstarting semi-products of the races. 

1. A method of manufacture of hollow, circular-shaped workpieces, comprising centrifugally casting hollow ingots from a bearing steel, reducing the ingot to form a tube, dividing the tube into sections, profile-forming the sections, then machining the formed sections by metal cutting methods, subsequently heattreating the machined formed sections to obtain optimum hardness, and after tempering finishing the product by at least one of the steps of grinding, superfinishing, lapping and polisHing.
 2. A method according to claim 1, wherein tubes obtained by rolling are divided into annuli by a cutting method for further processing to final products.
 3. A method according to claim 1, comprising removing the inner slag contaminated-layer from within the holes of the hollow workpieces prior to shaping them.
 4. A method according to claim 2, wherein the tubes obtained by rolling are divided into semi-products each of which serves for the fabrication of two or more parts.
 5. A method according to claim 2, comprising removing the inner slag-contaminated layer simultaneously with the dividing of the tube.
 6. A method according to claim 1, wherein workpieces made from chrome-steel are submitted to spheroidizing annealing, then machined by a metal cutting method, whereupon they are heated to austenitizing temperature for subsequent hardening.
 7. A method according to claim 1, wherein workpieces from chemically heat-treatable steel are first machined applying a metal cutting method, then the surface is submitted to a chemical heat-treatment with subsequent hardening and tempering.
 8. A method according to claim 1, wherein the races are profile-rolled with finishing allowances, after which they are heated to austenitizing temperature for subsequent hardening.
 9. A method according to claim 8, wherein the components are made from steel suitable for chemical heat-treatment and are formed by profile-rolling with finishing allowances.
 10. A method according to claim 1, in which bearing steels are used, and wherein a high-temperature mechanical treatment is applied, wherein the semi-products of the components are first heated to a temperature corresponding with the hardening temperature, then ring-forming is accomplished, with subsequent hardening and tempering.
 11. A method according to claim 1, in which bearing steels are used, and wherein a low-temperature mechanical treatment is applied, wherein the components are first heated to the austenite temperature zone, then cooled down to a temperature corresponding to approximately the longest latent period of the decomposition of undercooled austenite, after which the profile-forming with subsequent hardening are performed.
 12. A method according to claim 1, wherein the semi-products are formed by ring-forming at a temperature down to a temperature corresponding to the hardening temperature, after which they are machined in a hardened state using a metal cutting method, and then tempered.
 13. A method according to claim 1, wherein semi-products of components having a greater height, compared with the wall thickness of the final forging, are first die-forged to the required cross-section, after which they are turned through an angle of 90* between the bottom-die and the punch of a press ram within a single working stroke of the press ram and are sized in the bottom dead center of the ram stroke.
 14. A method according to claim 13, wherein annular shaped semi-products having a greater height compared to the wall thickness of the forging are first die-forged to a cross-section corresponding to the annulus of the outer bearing-races and partly to the annulus of the inner bearing-races, after which the thus obtained common blanks are sheared, the annulus for outer races is turned through an angle of 90*.
 15. A method according to claim 13, wherein annular shaped semi-products having a greater height compared to the wall thickness of the forging are first die-forged to a cross-section corresponding to the annulus of the outer bearing-races and partly to the annulus of the inner bearing-races, after which the thus obtained common blanks are sheared, the annulus for an inner race is inverted by an angle of 90* after the width had been die-forged to the required cross-section.
 16. A method according to claim 13, wherein the ring blanks are profile-rolled between rolls, whose operating surfaces are identical with the shape of finished races.
 17. A method according to claim 13, wherein the race blanks are die-forged in forming dies, whose operating surfaces are identical with the shape of finished races.
 18. A method according to claim 13, wherein the shape on the outer surface of the races is formed between profile rolls and the mandrel, the width and the hole through finished races being identical with the starting semi-products of the races. 